As techniques for coding still images and moving images, the JPEG (Joint Photographic Experts Group) technique, the MPEG (Moving Picture Experts Group) technique, and so on are used. For example, in the JPEG technique, a coding process is performed in such a way that a captured still image is divided into a block of 8×8 portions, and DCT (Discrete Cosine Transform) processing and quantization processing are performed on that block.
In the above-described coding process using DCT, there are cases in which, in order to reduce noise, a process for suppressing AC (Alternating Current) coefficients of luminance and color differences is performed. In a case where noise is reduced in such a manner, a problem arises in that block distortion sometimes occurs.